4. Phosphofructokinase (E_(3)) is the regulatory enzyme of glucose catabolism. This pathway produces ATP. If the concentration of ATP is high the synthesis of Fru-1,6-P is decreased. 1) What class of enzyme does phosphofructok inase belong to ? 2) What type of regulation has this enzyme? Describe the properties of such type of regulation. 3) Name the metabolites of this pathway which bind to the active and regulatory sites of the enzyme.

1) Phosphofructokinase (PFK) belongs to the class of enzymes known as transferases. Transferases are enzymes that catalyze the transfer of a functional group (such as a phosphate group) from one molecule to another.<br /><br />2) Phosphofructokinase exhibits allosteric regulation. Allosteric regulation is a type of enzyme regulation where the activity of an enzyme is controlled by the binding of a regulatory molecule (allosteric effector) to a site other than the active site. This binding causes a conformational change in the enzyme, which affects its activity.<br /><br />In the case of phosphofructokinase, it is regulated by ATP and AMP. When the concentration of ATP is high, it binds to the allosteric site of PFK, causing a conformational change that decreases the enzyme's activity. This reduces the synthesis of fructose-1,6-bisphosphate (Fru-1,6-P), thereby slowing down the glycolysis pathway and conserving glucose. On the other hand, when the concentration of AMP is high, it also binds to the allosteric site of PFK, causing a conformational change that increases the enzyme's activity. This promotes the synthesis of Fru-1,6-P and accelerates the glycolysis pathway, providing energy for cellular processes.<br /><br />3) The metabolites of the glycolysis pathway that bind to the active and regulatory sites of phosphofructokinase are:<br /><br />- ATP: ATP binds to the allosteric site of PFK, inhibiting its activity and decreasing the synthesis of Fru-1,6-P.<br />- AMP: AMP also binds to the allosteric site of PFK, activating the enzyme and promoting the synthesis of Fru-1,6-P.<br /><br />Other metabolites that can influence PFK activity include fructose-2,6-bisphosphate (F-2,6-BP), which is a potent activator of PFK, and citrate, which can inhibit PFK activity.